Method of treating cellulose compounds



e ucts.

Patented July 7, 1925 UNITED STATES PATENT oFFicE,

JOHN COLLINS CLANCY, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO THE NITRO-GEN CORPORATION, OF PROVIDENCE, ,RHODE ISLAND, A CORPORATION OF RHODEISLAND.

METHOD or TREATING 1 This inventlon relates to an imprbved method oftreating cellulose compounds, and has to do more particularly with theuse of an improved solvent for cellulose esters and the formationthrough the instrumentality of said solvent of a cellulose compoundpossessing certain new and useful properties by reason of which it iscapable of wide use in the arts. v I

While it is known that certain cellulose '20 esters, such for example,as certain of the acetates and nitrates, are soluble in certainsubstances such as acetone, amyl acetate, tetrachlorethane and carbonbisulfid, the use of these substances as well as other'solventsordinarily employed for this purpose is open to certain objections suchas the cost of the solvents, their infiammability, their poisonousnature and the difficulty experienced in removing the solvent from thefinal prod- Moreover, by no means all of the cellulose esters aresoluble in any of the solvents named, and each of the above solvents isadapted for use with only an extremely limited number of the celluloseesters included in the classes mentioned above.

One objectof the present invention is to provide a novel form of solventfor cellulose esters, including particularly the acetates 40 andnitrates, which is capable of more general use than those now employed,which is capable of being readily used without the exercise of the carenecessary in connection with some of those previously employed,

which is relatively non-inflammable and which is capable of beingreadily, separated from the resultant product.

Another object of the invention is to provide a novel method oftreatment for cellulose esters whereby they may be readily dissolved andthe cellulose compounds easily recovered from the solution and formedinto materials having extensive use in the arts,

CELLULOSE COMPOUNDS.

1921. Serial No. 482,173.

such, for example, as artificial silk, photographic films, etc.

A further object of the invention is to provide a new composition ofmatter capable of extensive use and having certain novel characteristicsnot generally possessed by the materials formed from methods hereto- 6ofore employed.

' Other objects and advantages of the invention relate to certain novelsteps and com- I binations of steps involved in the manufacture of thematerial as well as certain methods of combining the materials employedas will be more fully set forth in the detailed description to follow.

I have found that liquid anhydrous ammonia serves as an excellentsolvent for the re cellulose esters generally, being capable ofdissolvinga considerably greater number of the acetates and nitrates ofcellulose than any ofthe solvents previously used, while the nature ofthe ammonia is such as to perunit it to be readily removed from thecellulose compound by evaporation. By the use of liquid anhydrousammonia cellulose acetates and nitrates can be dissolved so as tocontinue to possess the structure of the orig- 8c inal celluloseacetates and nitrates without being degraded, that is, without losingtheir structural aggregates, thus forming a cellu'losetcompound whichcan be shaped into any desired form and still retain the-s5 strengthinherent in the original cellulose structure. 1

I propose to place the cellulose esters, such for example, as celluloseacetates, in a bath of liquid anhydrous ammonia, whereupon I no findthat they immediately dissolve to form a clear solution which can bereadily freed from air bubbles or entrained gases, and the solution thusformed may then be caused to fiow upon an endless belt, forced throughminute apertures or placed in moulds and the ammonia freed from thesolution by evaporation to form a transparent or translucent film,thread or other desired shape possessing a high degree of strength and10 capable of use for a variety of purposes.

Since anhydrous ammonia is liquefied only at comparatively lowtemperatures unless subjected to pressure in excess of that normallyexerted by the atmosphere I prefer to efi'ect the solution of thecellulose esters in muss-5 the resultant product.

the liquid anhydrous ammonia under a pressure somewhat greater than thatnormally exerted by the atmosphere and to evaporate normally exerted bythe atmosphere if desired, in orderto hasten the process. 1 prefer toeffect the removal of the ammonia. in an atmosphere from which moisturehas been excluded so far as practicable in order to prevent theformation of bubbles in the cellulose compound and thus obtain a moreuniform and high grade product. The ammonia used as a solvent can, ofcourse, be readily recovered.

Having found that the nitrates of cellulose as well as the acetates aresoluble in liquid anhydrous ammonia as above de scribed, I may utilizeliquid anhydrous ammonia for dissolving either cellulose acetates orcellulose nitrates separately or may mix cellulose acetates andcellulose nitrates in any desired proportions and. dissolve the mixturein ammonia to obtain a cellulose compound possessing certain desiredqualities when the solvent has been removed...

The product resulting from the treatment of cellulose esters as abovedesoribedepossesses certain advantages over similar products heretoforeformed by dissolving cellulose esters in the solvents previously used,-

by reason of the fact'that the liquid anhydrous ammonia may besubstantially entirely removed from the compound, whereas it has beenpractically impossible to entirely eliminate the solvents previouslyused from Moreover, the fact that the liquid anhydrous ammonia morereadily dissolves certain of the cellulose esters not heretofore readilysoluble in the solvents previously known imparts to the resultantproduct, by reason of'the inclusion of such esters therein, a structuralstrength not heretofore possible b the methods of treatment previouslyemp oyed.

As one illustration of an important application of my invention,photographic films as now used are formed from cellulose esters andcontain, when completed, silver salts and gelatine compounds. At thepresent time these films are generally burned after use to recover thesilver deposited therein, while'by the use of my improved method thecellulose esters of the film may be readily dissolved thfis permittingthe recovery of the cellulose for again forming a film and 'at the sametime recovering the metallic silver and gelatine compounds which are notacted upon by the ammonia.

Having described my invention, what I claim is:

1. The process which comprises, treating a cellulose ester with liquidanhydrous ammonia to dissolve the cellulose ester.

2. The process which comprises, treating cellulose acetate with liquidanhydrous ammonia to dissolve the same, and then acting upon the mass tosubstantially remove the ammonia therefrom.

3. The process which comprises, treating a cellulose ester with liquidanhydrous ammonia to dissolve the same, and then sub stantially removingthe ammonia therefrom under a pressure less than that at which thesolution was effected.

4. The process which comprises, treating cellulose acetate with liquidanhydrous ammonia to dissolve the same, and then substantially removingthe ammonia therefrom under a pressureless than that at which thesolution was efi'ected.

5. The process which comprises, treating a cellulose ester withliquidanhydrous ammonia to dissolve the cellulose ester, and thensubstantially removing the excess ammonia with exclusion of moisture.

6. The process which comprises, treating cellulose acetate with liquidanhydrous ammonia to dissolve the cellulose acetate, and thensubstantially removing theexcess ammonia with exclusion of moisture.

7. The process of treating a cellulose compound which comprises,subjecting cellulose acetate to the action of liquid andhydrous ammonia.

8, The process of treating a cellulose compound which comprises,subjecting a cellulose ester to the. action of liquid anhydrous ammoniaunder super-atmospheric pressure.

9. The process of treating a cellulose compound which comprises,subjecting a cellulose ester to the action of liquid anhydrous ammoniaunder super-atmospheric pressure,

and then ammonia.

10. The process of treating a cellulose compound which comprises,subjecting cellulose acetate to the action of liquid ammonia undersuper-atmospheric pressure.

' 11. The process of treating a cellulose compound which comprises,subjecting cellulose acetate to the action of liquid ammonia undersuper-atmospheric pressure, and subsequently substantially removing theammoma. i

12. The process of treatidga cellulose compound which comprises,subjecting a cellulose ester tolthe action of liquid anhydrous ammoniaunder super-atmospheric substantially removing the sure, and thensubstantially removing the ammonia therefrom with exclusion I ofmoisture.

14;. The process of treating a cellulose compound which comprises,subjecting a cellulose 'ester tothe action of liquid anhydrous ammoniaunder super-atmospheric pressure, and then substantially removing theammonia therefrom under a pressure less than that under which thesolution was eliected.

15. The process of treating a cellulose compound which comprises,subjecting cellulose acetate to the action of liquid anhydrous ammoniaunder super-atmospheric pressure, and then substantially removing theammonia therefrom under a pressure less than that under which thesolution was efiected. I

16. The process of treating acellulose compound which comprises,subjecting a cellulose ester to the action of liquid anhydrous ammoniaunder super-atmospheric pressure, and thensubstantially removing theammonia therefrom under a pressure less than that under which thesolution was effected and with exclusion of moisture.

17. The process of treating a cellulose compound which comprises,subjecting cellulose acetate to the action of liquid anhydrous ammonia,under super-atmospheric pressure, and then substantially removing theammonia therefrom under a pressure less than that under which thesolution was efl'ected and with exclusion of moisture.

In testimony whereof I have aflixed my signature.

JOHN COLLINS CLANCY.

